1. Field of the Invention
This invention relates to a focusing apparatus for an optical apparatus, and more particularly to a focusing apparatus for moving the observation member of an optical apparatus to focus it on an object.
2. Related Background Art
In a moving apparatus for focusing according to the prior art, there has been proposed a focusing apparatus, i.e., a lens barrel moving mechanism, as shown, for example, in FIGS. 3 and 4 of the accompanying drawings. The prior art will hereinafter be described with reference to FIGS. 3 and 4.
In FIGS. 3 and 4, a microscope body 1 is provided with a microscope body portion 2 including an optical system necessary for observation, a stand 3 and a lens barrel moving mechanism 4 which is a focusing apparatus.
The microscope body portion 2 has a lens barrel case 7 in which there are provided an eyepiece unit 8, an objective lens unit 9 and an illuminating device 10. A transparent plate (e.g. an acryl plate) 11 is mounted in the direction of illumination of the illuminating device 10. The illuminating device 10 can illuminate a specimen, not shown, placed on the stand 3 through the transparent plate 11. The turning on and off of the illumination is effected by operating a switch 12.
A hollow shaft 13 is fixed to that side 2a of the microscope body portion 2 which is adjacent to the lens barrel moving mechanism. The hollow shaft 13 is rotatably held by a bearing (not shown) provided in the front side holding case 41 of the lens barrel moving mechanism 4. A disc member 16 having a diameter larger than the diameter of the bearing is fixed to that end surface of the hollow shaft 13 which faces the inside of the front side holding case 41. The hollow shaft 13 and the disc member 16 are fixed to the side 2a of the microscope body portion 2 at three locations on a phantom circumference by three screws 17. Thereby, the microscope body portion 2 can be rotated about the axis of the hollow shaft 13. The microscope body portion 2 and the disc member 16 are connected together so as to sandwich the vicinity of the bearing of the front side holding case 41 from the opposite sides thereof and therefore, it never happens that when the microscope body portion 2 is rotated, the hollow portion 13 axially deviates. Also, during the microscopy and containment of the microscope, the microscope can be fixed at a predetermined position by a positioning mechanism (not shown).
The lens barrel moving mechanism 4 has a holding case comprising the front side holding case 41 and a rear side holding case 42, a guide plate 27 vertically fixed to the stand 3, and an operating handle 43 (in FIG. 3, a rotary shaft 44 to which the operating handle 43 is fixed and a rubber roller 30 are shown in cross-section).
The rubber roller 30 is mounted on the rotary shaft 44. A resin plate 28 contacting with the rubber roller 30 is secured to the guide plate 27. Also, a resin plate 34 contacting with the back of the guide plate 27 is secured to the inner side of the rear side holding case 42. That surface of the resin plate 28 which contacts with the rubber roller 30 is knurled.
The lens barrel moving mechanism 4 is further provided with bearing members 45a and 45b for rotatably holding the opposite end portions of the rotary shaft 44, an adjusting screw 35 screwed into the front side holding case 41, and a U-shaped pressing member 33 curved in conformity with the configuration of the rubber roller 30. Through-holes 36a and 36b are formed in the opposite sides of the holding case. The bearing member 45a is inserted in the through-hole 36a while overlapping the end portion 33a of the pressing member 33. Also, the bearing member 45b is inserted in the through-hole 36b while overlapping the end portion 33b of the pressing member 33. Each of the through-holes 36a and 36b is a plot slightly extending in a direction orthogonal to the guide plate 27 and guides the opposite end portions of each bearing member and the pressing member 33 in said direction.
The central portion of the back of the pressing member 33 is always pressed by the adjusting screw 35, and the bearing members 45a and 45b are pushed into the guide plate 27 side along the respective through-holes by the opposite end portions of the pressing member 33. A force resulting from this is applied to the rotary shaft 44 held by these bearing members and presses the rubber roller 30 against the resin plate 28. By the adjusting screw 35 pressing the pressing member 33, the resin plate 34 of the rear side holding case 42 is also pressed against the back of the guide plate 27.
Since a force is acting on each member as described above, a predetermined frictional force is created between the rubber roller 30 and the resin plate 28 and between the back of the guide plate 27 and the resin plate 34. Accordingly, when the operating handle 43 is rotated, the rubber roller 30 is moved along the resin plate 28 in conformity with the direction of rotation of the operating handle 43, and therewith, the front side holding case 41 and the rear side holding case 42 themselves holding the operating handle 43 are also moved.
That is, if the operating handle 43 is rotatively operated to vertically move the microscope body portion 2, the focus adjustment of the specimen placed on the stand 3 can be effected.
When it is desired to adjust the aforementioned frictional force, the adjusting screw 35 is operated. If, for example, it happens that as the present stereomicroscope is used for many years, the rubber roller 30 idly rotates relative to the resin plate 28, the adjusting screw 35 is rotated in a predetermined direction and screwed in to thereby bring the pressing member 33 close to the guide plate 27. Thereby, the previous frictional force can be revived.
When conversely, the operating handle 43 is stiff, the adjusting screw 35 is rotated in the opposite direction and moved in a direction to be pulled out, thereby keeping the pressing member 33 away from the guide plate 27. If this is done, the aforementioned frictional force will be decreased and the operating handle 43 will become light.
In such prior art, the lens barrel moving mechanism sandwiches the guide plate between the rear side holding case and the rotary shaft by the use of simple members such as the resin plate, the rubber roller, the pressing member and the adjusting screw. The sandwiched guide plate makes frictional contact by the contact of the resin plate it has with the rubber roller mounted on the rotary shaft and the engagement thereof with the resin plate the rear side holding case has. By such a simple construction, it is made possible to obtain a frictional force easily and the movement of the microscope body portion is reliably effected.
However, there has been the problem that if in an actual state of use, the cumulative frequency of the movement of the microscope body portion by many years of use becomes enormous, the contact pressure decreases and the operating bundle becomes light. At such a time, the adjusting screw can be rotated in a predetermined direction and screwed in and the pressing member can be brought close to the guide plate to thereby revive the previous frictional force, but there arises the necessity of avoiding such work as far as possible. In the prior art, however, the construction is simpler and this has limited the durability thereof.